Radio communication transmitting and receiving combination



Jan. 16, 1951 F. M. DAVIS 2,537,972

RADIO COMMUNICATION TRANSMITTING AND RECEIVING COMBINATION Filed Aug. ll, 1944 6 Sheets-Sheet l E F jpl 9m/@74 5777797777@ G Wadi/@752' iffz/U/f jyW/g-[Zf TMW??? mi HTI i I /v 0 l dJ/ l d i 727m e `j?? Z 0xff/a? jrr #7W/572227" J I I fr f l fr f/'zm/O j, I?? V2/'teni y//z/'ef f7@ @0 W fw/6er am?? W 6 Sheets-Sheet 2 F. M. DAVIS AND RECEIVING COMBINATION RADIO COMMUNICATION TRANSMITTING Jan. 16, 1951 :med Aug 11 1944 Jan. 16, 1951 F. M. DAvls 2,537,972

A RADIO COMMUNICATION IRANSMIIIING AND RECEIVING COMBINATION Filed Aug. 1l, 1944 6 Sheets-Sheet 3 L[VMM/wv VAVAIIAVAVAVAVA l 5 l C i 101m.) g im Jan. 16, 1951 F. M. DAvls 2,537,972

RADIO COMMUNICATIONIRANSMITIING ANO RECEIVING COMBINATION Filed Aug. I1, 1944 6 sheets-sheet 4 aff? Jan. I6, 1951 F M DAVIS 2,537,972

RADIO COMMUNICTION TRANSMITTING AND RECEIVING COMBINATION Filed Aug. 11, 1944 6 Shee ts-Sheet 5 Jan. 16, 1951 F. M. DAVIS 2,537,972

RADIO COMMUNICATION IRANSMITIING AND RECEIVING COMBINATION Filed Aug. 11, 1944 I e sheets-sheet 6 I@ nl",

AAAAAAML VVVVVVVV QYQU Tl- Patented Jan. 16, 195i RADIO COMMUNICATION TRANSMITTING AND RECEIVING COMBINATION Frank M. Davis, Cedar Rapids, Iowa, assignor to Collins Radio Company, a corporation of Iowa Application August `11, 1944, Serial N o. 548,978

13 Claims.

This invention relates to a radio transmitting and receiving combination, and more particularly to a system using a common tunable oscillator for both transmission and reception.

One feature of this invention is that it provides an improved radio combination system for transmitting and receiving; another feature of this invention is that a single tuning means effects coordinated selection of the desired frequency in both the transmitting and receiving portions of the system; still another feature of this invention is that transmission and reception on the same frequency are ensured despite variation of the tunable oscillator from its calibrated frequencies; yet another feature of this invention is that the system is quickly and conveniently tunable to any desired frequency in any of a plurality of frequency ranges, so that transmission and reception on such frequency may be effected; a further feature of this invention is that spurious frequencies are minimized; still a further feature is that antenna tuning and loading adjustments may be made with the transmitter inactive, ensuring transmission at or near peak power immediately upon coming on the air; and yet a further feature of this invention is that the tunable oscillator may be used to provide a beat note for CW reception. Other features and advantages of this invention will be apparent from the following specification and the drawings, in which:

Figure 1 is a block diagram of one system embodying my invention; Figure 2 is a block diagram of an improved form of a system basically similar to that shown in Figure l; Figure 3, comprising the portions 3a and 3b, is a circuit diagram of an operable embodiment of a transmitter-receiver combination system corresponding to the block diagram of Figure 2; Figure 4 is a block diagram of a preferred embodiment of my invention; and Figure 5, comprising the portions 5a, 5b and 5c, is a circuit diagram of an operable embodiment of a transmitter-receiver combination system corresponding to the block diagram of Figure 4.

Two-way radio communication is becoming of increasing importance, and under many circumstances it is desirable to have the transmitt'ng and receiving equipment tunable over a desired frequency range, or a plurality of frequency ranges. Under such conditions the transmitted frequency cannot be crystal controlled, but must have a frequency controlled by a tunable oscillator tank circuit. Despite the greatest care in design and construction, an oscillator tank circuit undergoes frequency changes as the result cf its exposure to variations in temperature, humidity, etc., and this makes it difficult to determine accurately, by any system of dial calibration, the frequency being transmitted or received, particularly in the higher frequency bands, as those used in aircraft Work.

I have devised and am here disclosing a singlecontrol (in so far as tuning is concerned) radio transmitting and receiving combination system wherein transmission and reception on t-he same frequency are ensured. This enables an operator to tune in on another station Which is transmitting, and then to go on the air himself as soon as the other station ceases transmission with full assurance that his signal is on the same frequency as that on which the other station was transmitting, regardless of the setting of his tuning dial or the accuracy of its calibration. I am here disclosing several systems for accomplishing the desired results, all of these systems making use of the same tunable oscillator in both tra s i mission and reception. In the systems shown in Figures 1 3, the tunable oscillator is used directly for one operation (either transmission or reception), and in combintion with a xed frequency oscillator in the other operation. In the systems shown in Figures 4 and 5, one :multiple of the oscillator frequency is used during transmission and a different multiple during reception. In connection with all of these systems, the desired wave is amplified and transmitted in the one case; while in the other case, in order to receive onthe same frequency, the different or displaced frequency generated by means including the tunable oscillator is used as the local or heterodyning wave of a super-heterodyne receiver having its intermediate frequency amplifier tuned to a frequency representing the -difference between the initial or transmitted frequency and the displaced frequency.

The` basic concept of having a single tunable oscillator operating as all or part of the wave generating means during both transmission and reception is capable of embodiment not only in the systems shown here, but also in other systems ensuring transmission and reception upon the same `frequency provided the tunable oscillator is left at the same setting. Other systems for accomplishing this purpose are to be found in my own co-pending application Ser. No. 524,205, filed Feb. 28, 1944, Patent No. 2,402,606, issued June 25, 1946, with claims to a different specific system not in this application; and in the cio-pending applications of Arthur A. Collins, Ser. No.

524,204, filed February 28, 1944, Patent No. 2,447,490, issued August 24, 1948, and of Melvin L. Doelz, Ser. No. 524,206, Patent No. 2,457,134, issued December 28, 1948, filed February 28, 1944; and certain features disclosed and originally claimed here are the subject matter of my divisional application Serial No. 685,934, filed July 24, i946.

lvfy basic concept is .to provide radio apparatus comprising, as its principal elements, variable wave generating means for providing desired waves of an initial frequency variable over a predetermined range, or a plurality of ranges; means associated with and including said wave generating means for providing other desired waves oi' a frequency displaced Hom said initial frequency but bearing a predetermined relation thereto; means for amplifying and transmitting one of the desired waves, as that on the initial frequency; and a super-heterodyne receiving system having an intermediate frequency amplier tuned to the difference between the frequencies of the two desired waves, the other of said desired waves, as the displaced frequency waves, serving as the local heterodyning waves for the receiving system. Where the relation between the initial and displaced frequencies is one of a fixed frequency differential, the intermediate frequency amplifier of the receiving system is tuned to this xed frequency. Where the relation between the initial and displaced frequencies is a matter of fixed percentage of the initial frequency, and thus varies in absolute frequency with variation in the initial frequency, the intermediate frequency amplifier of the receiving system is tunable over a range determined by the range of tuning of the variable wave generating means, and the tuning of the intermediate frequency amplier and the wave generating means are ganged. In any event, when one has ceased listening to a given signal or a given frequency, switching over to transmission Without touching the tuning control ensures sending on the exact frequency of the signal previously heard regardless of any differences ybetween actual oscillator frequency and dial calibration; and conversely, when one has ceased transmitting, switching over to reception (which effects the desired displacement of frequency among other things) without touching the tuning control ensures reception on the exact frequency being previously transmitted.Y The advantages in two-way communication at any of a large number of frequencies throughout one or more bands is obvious.

While l am terming the systems disclosed here single-control systems, it will be understood that this merely means that there would be only a single tuning control for both the transmitting and receiving portions of the radio apparatus, which would normally be housed in a single cabinet. in addition, of course, a commercial set would include a band switch, antenna coupling and loading controls, an ori-oil switch or several of such switches, a beat frequency oscillator control, a manual volume control for the receiving portion of the system, etc. The switch-over from transmission to reception would normally be effected by a keying relay, or by a push-buttonoperated relay associated with the microphone of the transmitter. With a system of this kind no matter how inexperienced the operator may he, once he finds and hears a given station (whether it be another airplane, a ground station or the like) he is sure to be able to talk to it, sure to be on the frequency to which the receiver of that other station is tuned. Another advantage is that this system enables the same antenna tuning and loading circuit to be used for coupling both the transmitter' and receiver to the antenna, so that the antenna can be tuned during reception, without breaking radio silence, with assurance `that transmission will be at or very near maximum possible power immediately upon initiation of transmission, without less of time for adjustment of the antenna tuning and loading controls after transmission has been started, this being one of the features claimed here.

In the particular embodiment oi invention illustrated in the block diagram of Figure l, a tunable oscillator A delivers its output to a multiplier B, to provide wave bands over which `the set may work, the oscillator and multiplier comprising means for generating waves of any desired frequency in any of a plurality of bands, the multiplier (in practice comprising a plurality of multiplying sections) providing an output which bears a relation to the oscillator output resulting from multiplication by a factor which may be anything from unity to about twenty. The output of the multiplier B is delivered to a mixer C where it may be combined with the wave output of a fixed oscillator D, or not, as be desired. ln the particular system illustrated the wave output of multiplier B and that of the fixed oscillator D are combined during transmission. One of the resultant waves in the output of the mixer (as, for example, a frequency equaiing the sum of the frequencies provided by the multiplier and the fixed oscillator) is delivered to an amplifier E. The output of this amplifier is delivered to the power amplier F here shown as having its output varied by action of the modulator G in accordance with voice sounds supplied to the microphone associated with this modulator, for example. During transmission the modulated output of the power amplifier F is delivered to the antenna tuning and loading netwo; nere identined as l-l and then supplied to an appropriate antenna system.

Change-over between transmission and reception is here shown as accomplished by two movable two-position switches identified as O and P. The switch O has its movable element connected to the antenna and its tuning and loading network, and is adapted selectively to make connection either with the output of the power amplifier F for transmission (the switches being shown in the transmitting position in solid lines and in the receiving position in dotted lines), or to an RF amplifier J, forming part of the receiving system, during reception. The switch P has its movable element connected to the output of the fixed oscillator D, and is arranged to connect this to the mixer C during transmission, and to connect it to the detector L of the receiving system, through an on-cif switch N, so that the fixed oscillator may be used as a beat frequency oscillator during tuning or during code reception.

When the change-over switches O and l? are in their other or dotted line positions, the transmitting portion of the system is disconnected from the antenna and this and its tuning and loading network are connected to the input of the radio frequency amplifier J as mentioned before. The output of this amplifier is delivered to the mixer C where it is heterodyned with the wave produced by the tunable oscillator and multiplier B, the Wave from the fixed oscillator D being no longer supplied to the mixer C. The output of the mixer C is then delivered to the intermediate frequency amplifier K which would, in this case, be fixedly tuned to the frequency of the fixed oscillator D. The output of the intermediate frequency amplifler is delivered, in conventional manner, to the detector L and an audio amplifier M, and then to any conventional translating means (not shown), as a speaker or earphones. In order to simplify control ofthe radio apparatus, the change-over switches are ganged, as indicated; and all of the necessary tuning controis, as those in the portions identified as A, B, E, F, H and J, are also ganged so that` tuning may be effected by a single control knob. The particular tuning referred to in this latter case, of course, is tuning of the variable reactance element in each of the tank circuits, as different fixed reactance elements may be used in various tank circuits in different bands, switching between bands being effected in conventional manner with a band switch, not shown.

For the purpose of illustrating the operation of such a system as that shown in Figure 1, it may be assumed that the tunable oscillator A is so designed as to provide waves of a frequency variable over a range from 1,000 to 1,500 kc.; and that the multiplier B is adapted to pass the waves with a unity multiplication factor, to double their frequency, or to triple it. This would provide three bands, one being from 1 to 11/2 megacycles, another from 2 to 3 megacycles, and the third from 3 to 41/2 megacycles, speaking with respect to the output of the multiplier B. An appropriate frequency for the fixed oscillator D is 455kc. If it be assumed that the frequency during transmission is the arithmetical sum of the multiplier output frequency and the fixed oscillator frequency, it will thus be seen that the transmission bands covered would be 1,455 kc. to 1,955 kc. as the first band; 2,455 kc. to 3,455 kc. as the second band; and 3,455 kc. to 4,955 kc. as the third band.

If We then assume that the tunable oscillator is tuned to its lowest frequency of 1,000 kc., and the tuned circuits in the multiplier are so chosen that the multiplication factor is unity, it will be apparent that transmission will take place on 1,455 kc. When the operator has finished transmitting he may, without touching the tuning control, switch over from transmission to reception merely by Vthe automatic operation of the relay effecting ganged or synchronized operation of the change-over switches P and O. Throwing of these switches to the dotted line positionwould disconnect the fixed oscillator from the mixer C and connect the antenna system to the input of the RF amplifier J. A 1,455 kc. signal coming into the RF amplifier would then beheterodyned in the mixer C with the 1,000 kc. Waves supplied by the multiplier B, and the difference between these frequencies would be 455 kc. It is thus obvious that if the intermediate frequency amplier K is xedly tuned or peaked to a 455 kc. frequency, the same frequency as that of the fixed oscillator D, the signals received will be exactly on the same frequency as those trans.

mitted. The xed oscillator D can be very highly stabilized, by use of a crystal or otherwise; and any differences between the actual and dial frequencies of the tunable oscillator are identical on both transmission and reception. Moreover, when the change-over switch P is in the reception position, closing of the switch N enables the fixed oscillator D to be used as a beat noteoscilplished in lator is desired. By use of this beat note oscil lator tuning to a received signal can be very accurately effected, as it is only necessary to tune until there is zero beat with the desired signal; or, if `code is being received, the tuning control can be operated to detune very slightly (say 500 to 1,000 cycles), whereupon the fixed oscillator D will provide the desired beat note.

It will thus be seen that the wave generating means comprising the tunable oscillator A and the multiplier B together with the xed oscillator D, provides an initial frequency, fol' transmission, of 1,455 kc. The Waves to be transmitted are what may be termed one set of desired waves; and the waves to be used as local heterodyning waves for reception may be termed the other set of desired waves. This other frequency is effected merely by cutting out the fixed oscillator D upon `change--over from transmission to reception, this displacing the frequencies of the locally generated waves from 1,455 kc. to 1,000 kc. In the particulal1 situation here described, and in the system illustrated in Figure 1, the displacement is a xed frequency displacement regardless of the initial setting or frequency of the tunable oscillator A. In this regard it will be understood that the word displacement is intended broadly to cover either an increase or a decrease of frequency. For convenience of description, the frequency used for transmission is being termed the initial frequency, and the different frequency used for local heterodyning purposes during reception is being termed the displaced frequency, although these words are intended broadly enough, in the claims, to include a situation wherein the local frequency during reception might be termed the initial frequency and that used for transmission the displaced frequency. Moreover, while a separate xed oscillator is shown as the means for displacing the frequency of the desired waves, it will be understood that this can be accomother ways. In the system shown in Figure 1, for example, the fixed oscillator D l could be eliminated and the RF' amplifier could be caused to oscillate during transmission to provide the desired additional frequency source. Also, as is shown in the systems hereinafter to be described and in the systems forming the subject matter of the other co-pending applications mentioned earlier, the displacement of the frequency of the desired waves can be effected in a number of different ways. My basic concept lies in using the same tunable oscillator as part of wave generating means providing one desired frequency for transmission and another desired frequency as the local heterodyning wave for reception, there being a predetermined relation between the initial and displaced frequencies.

During reception, under the conditions assumed above, the received frequency is a function of the fixed frequency derived from the fixed oscillator D and a frequency which is some multiple of the frequency to which the tunable oscillator A is tuned. At certain points in the tuning range in each band, unless great care is taken'in the selection of the frequencies and the width of the bands, the reception frequency will heterodyne with some other multiple of the basic tunable oscillator frequency. 'Ihe system is operable without such heterodyne interference during reception, if the xed oscillator frequency is chosen such that itis considerably less than the minimum frequency of the tunable oscillator. Under these conditionsrhowever, the

transmitter will have -certain vspurious radiations, the more 'serious being radiations at the multie plier output frequency plus or minus multiples of the Jxed oscillator frequency.

I find that the operation of a system such as described in Figure l can be 'considerably improved by combining the multiplier output waves and `the nxed oscillator waves, 'during trenisn'iis` sion, in a balanced mixer 'so designed that the spurious radiations mentioned inthe preceding paragraph (multiplier output plus or minus multiples of the fixed oscillator frequency) are balanced out; by working the mixer tubes substantially above cut-off level; and by designing the fixed oscillator to be as free of harmonics as possible. A system of this type, basically similar to but representing an. improvement on the system just described, is illustrated 'in block vdi'- agram form in Figure 2 and in circuit diagram form in Figure 3.

Referring now more particularly to the block diagram comprising Figure 2, it will be seen that the system there shown is basically similar to that 'shown and described earlier, and the description of Figure 2 will therefore be kept brief. In the system in this latter figure a tunable oscillator A" supplies waves variable over a certain frequency range to a multiplier B' enabling the set to cover different bands. The' output of the multiplier B' is connected to the movable element of a two-position switch here identified as Q', this switch being ganged with the other two change-over switches O' and P' associated with the antenna tuning network H' and the fixed oscillator D', respectively. When :f

the switch Q' is in transmitting position, as is shown in solid lines, the output of the multiplier B' is delivered to the balanced mixer R', where it is combined with waves delivered from 'the fixed oscillator D. The desired balanced `mixer output is then delivered to a power amplifier F (preferably through 'pre-amplifying stages inpractice) where it is modulated by voice sounds by the modulator G'. With the switch O 'in transmitting position, 'as illustrated, the antenna and loading network H' and the antenna are connected to the output of the power amplifier F' and the modulated waves 'are transmitted. The use of the balanced mixer R' for combin ing the wave outputs of the multiplier Bl and the fixed oscillator D enables suppressionl of stronger undesired spurious waves.

On the other hand, when the change-overl switches are all thrown to the receiving position shown in dotted lines, the antenna system H' is connected to the input of the RF amplifier J'; the output of the multiplier B is connected to another mixer S'; and the output of the fixed oscillator D' is made available for beat note oscillator purposes, this latter use being under the control of the switch N'. Removal of the fixed oscillator output from those parts of the circuit where it has any eifect on the output of the multiplier B' effects a displacement of the desired waves by the desired fixed frequency, and the displaced waves are heterodyned with the incoming sgnal in the mixer S', the desired resultant intermediate frequency waves being then ampliied in the intermediate frequency amplier and given further amplification in the audio ampliiier M. it will be noted that the system just described differs from that shown in Figure 1 primarily in the use of two separate mixers R andl S' in piace of the single mixer C shown K', demodulated in the detector L',

Figure fl.; 'and in making R a balanced mixer to Suppress 'certain undesired components which would otherwise 'appear as spurious radiations during transmission.

Referring Snow more particularly to the circuit diagram of Figure A3 (comprising portions 3a and 3o) the portions corresponding to the various rectangles and switches vof the block "diagram of Figure 2 are 'siinla'ilyY lettered The tunable oscillator -A' is shown comprising a( tube IU, which be or tube type No. esJ'z, .having fa tari-1' oiro'u'it 'e(rnr'ir-iSing 'permeability turl'ed variatie indu'c'tanoe lil and 'a lnx'ed condenser t2.. While the tuned tank circuits throughout the system are shown `as having fixed condensers (fixed except for such slight variations as may be desirable for vtrimming purposes) 'and variable inductances, it will be understood that the principles of 'operation of my system are equally applicable to circuits where the inductances are fixed and `are tuned by variable condensers.

The output of the oscillator A' is'here lshown as coupled to a 'grid of the multiplier B', here shown as comprising the tube l 3, which may also be of tube type No. GSJ'i, and its associated tuned circuits'. The tank circuit in the 'output of the 'tube I3 Ais here shown as comprising the variable o'r tunable coil l having selectively associated therewith (in accordance with the position of the band switch I5) 'a selected one of the xe'd 4co'ndensers ita-ec. The selected output of the multiplier B' is deiivered to the changeover switch Q which is adapted to supply the waves thus generated to the balanced mixer R" during transmission (through the wire bv leading from Figure 3a to Figure 3o), when the switch is in the position shown in 'solid lines, o-r to the mixer S in the receiving portion of the system when the switch is in the position shown in dotted lines.

Still referring 'to Figure 3a, the fixed oscillator D' is `also adapted to supply wa'ves to the balanced mixer R during transmission. This nxed frequency generator D Iis here shown as comprising the tube il, which may be of 'tube type No. 6.35, having associated therewith a tank circuit comprising the fixed induct'ance I 8 and the xed condenser I'S, it being understood that in practice a crystal may be used in conventional manner to stabilize the oscillator at the desired frequency, as 455 kc. vThe output of this fixed oscillator is connected to the movable element of the change-over switch P where it is adapted, when the switch is in the .position shown in solid lines, to be delivered to the balanced mixer through the wire lc forming one of the connections between the portions 3a and 3o of the circuit diagram. In the other or dotted line position of the changeover switch used during reception., the output of the fixed oscillator is delivered to one terminal of the on-oi vswitch N' having its other terminal connected to the anode of the detecting arrangement L', 'so that the fixed frequency oscillator may be used as a beat frequency oscillator when the switch N'v is in the on position.

Assuming that the change-over switches are all in the transmitting position (as illustrated in solid lines), and referring now more particularly to Figure 3o, the operation of the system during transmission will be described. The balanced mixer R' (which might also be termed a balanced modulator, although it is not so termed here because it is not performing the function of signal modulation) i's here shown as comprising the tubes 2l 'and 2'2, which may be of tube type No.

GSA?, connected in conventional manner for balanced mixing. In this case the output of the ixed frequency oscillator D (delivered through the wire c) is connected in push-pull to the grids 2 la and 22a of these tubes; and the wave output of the multiplier B' (delivered through the Wire b) is connected in direct or similar phase relationship to the grids Zib and 22h. It is found preferable to connect the tunable wave directly to the corresponding grids, and to keep its energy level substantially lower than that of the wave output of the xed frequency oscillator. The plates of the tubes 2| and 22 are connected in push-pull relation to a tuned output circuit comprising the variable inductance 23 and two capacity systems connected to ground and to opposite sides of the coil 23. The upper capacity system (here so termed because of its position on the drawing) comprises the condensers Zita-c, selection of a diierent one of these condensers on each band being effected by the band switch 25. The other capacity system comprises a corresponding set of iixed condensers 26ac selected by the band switch 2l, and a condenser 23 used to balance the grid capacity of the succeeding tube into which this output system works.

This succeeding tube is a driver or pre-amplifier stage in the power amplier F, here com- `prising the tube 29, which may be of tube type No. 6SJ7. The output circuit of this tube includes a tuned tank circuit comprising the variable inductance 3i] and one of the condensers 3Iac selected by the band switch 32. While the distribution of these elements throughout the circuit diagram renders it impossible to indicate on the circuit diagram, it will be understood that all band switches in the system are ganged on a single shaft in conventional manner; that all change-over switches are synchronously operated as indicated in the block diagram of Figure 2, as by being relay operated or by being ganged on a single shaft; and that all ofthe variable elements in the tuned tank circuits are also appropriately ganged, as indicated in the block diagram of Figure 2, in conventional manner, so that they may be operated by a single tuning knob.

The output of the tube 29 is delivered to the power output stage here shown as comprising the tube 32, which may be a pliotron of tube type No.

807, although it will be understood in practice that power requirements will indicate `the type of tube, the number of preamplifying stages, etc., in the power amplier. The carrier wave delivered to the tube 32 by the preceding portions of the system, as described, is modulated in desired manner by plate modulation effected by a modulating arrangement here shown as comprising tubes 33 and 34. The space current of the tube 33 is here shown as affected by voice waves picked `up by a microphone 35, although it will be understood that keying or other modulation may be used. The output of the tube 33, which may be of tube type No. 6J5, is delivered to the tube 3ft, which may be of tube type No. 807, for further power ampliiication and the desired modulating effect on the output of the tube 32.

The modulated output of the tube 32 is delivered, when the change-over switch O is in the transmitting position shown in solid lines, to the antenna tank circuit comprising the variable in-` ductance 35 and whichever one of the ilxed condensers Sta--c is selected by the band switch 3l. This is coupled, particularly where it is to be used with a relatively short antenna, as in aircraft work, to antenna loading means; here shown as comprising a variometer 38 and an inductance or capacity provided by the tapped loading inductance 39 or the loading condensers 4tac (selected by the tap `switch 4l) to the antenna here indicated diagrammatically as 42. The arrangement of this tuning and loading system between the change-over switch O and the antenna 42 is Very advantageous. This enables the tuning and loading means H' to be used for both transmission and reception, not only avoiding duplication of circuit elements but also enabling the system to be adjusted, during reception, so that transmission can be` initiated, without further adjustment of the system, at very close to maximum possible power. This is, of course, highly important in radio equipment designed for naval aircraft, for example, where it is undesirable to break radio silence until the actual instant of transmission of an important message, it being undesirable to turn on the transmitter in advance and adjust the tuning and loading controls of the antenna system. With this arrangement, an airplane provided with my equipment can tune the radio apparatus to a transmitter on the frequency at which it is subsequently desired to transmit, as a transmitter at a home base. With the band and frequency thus determined by setting of the band switches and ganged tuning controls, the coupling between the coil 35 and its associated coil may be setirom a chart, or set by starting with loose coupling and working up slowly to an approximately correct setting, asthe coupling setting is not particuf larly critical; and then the loading control comprising the tap switch 4i and the vaiometer 33 may be adjusted until the loudest signal is being received. The antenna tuning and ,loading system is then properly adjusted, and throwing the system over to transmission enables going on the air with very close to the maximum power in the antenna. Operation in this manner has proved to provide antenna coupling and loading settings always providing at least of the maximum power in the antenna possible by careful adjustment of the controls with the transmitter on, and generally in the neighborhood of of this maximum power. Where it is desired to subsequently transmit on a predetermined frequency on which no station is sending, the same thing can be done by setting the band switches and tuning controls to the desired `frequency as determined from the indicating means associated therewith, and using received noise as means for adjusting the coupling and loading controls. i

When the change-over switches O' P and Q are in the receiving position indicated in dotted lines, the antenna tuning and loading system is connected (through the wire indicated as a) to the radio frequency amplifying portion J' of the. receiver. This is here shown as comprising a tube 42, which may be of tube type No. ESSK'l,

having its input tuned by the tank circuit comprising therinductance 35 and one of the condensers 33e-c and its output tuned by the tank circuit comprising thevariable inductancefi-t and which ever-one cf the xed condensers lila-c is selected by the band switch 45. The output of this radio frequency stage and the output of the multiplier tube I3 (referring now more particularly to Figure 3a) are both delivered to a mixer or rst detector here shown as comprising the tube 43, which may be of tube type No. 6SJ7. The desired one of the resultant waves,`

here assumed to be the difference between the incoming signal and the waves delivered by the tube i3, is then selected by the xedly tuned intermediate frequency amplier K' here shown as comprising the three fixedly tuned 'inter-mediate frequency transformers (tuned to 455 kc. under the conditions assumed earlier) 4l, 48 and 49, and the tubes 50 and 5i, which may be of tube type No. GSK'?. The output of the intermediate frequency amplifier is here shown as delivered to vsecond detector and rst audio amplifying arrangements incorporated in a single envelope in the tube here identied as '52, which may be of tube type No. BSQ?. The rectified and amplified 'audio output is here shown as delivered to earphones 53, although it will be understood that in commercial practice additional stages of audio amplification might precede this translating device. If the `incoming signal comprises code (CW), the desired audio note is provided by turning the switch N to the on. position to use the output of the tube il for beat frequency oscillator purposes, the tuning control being slightly detunzd as described earlier. The reactance and resistance values, tube supply voltages, etc. would be determined in conventional manner by the frequency bands on which the apparatus is designed to operate, and by the type of tubes used and the function to be performed by the tube in each case, and will not be ldescribed in detail in connection with this particular system.

Another embodiment of my basic invention, one which ,I consider a preferred embodiment and lwhich is 'believed by me to be superior :to other specific embodiments of `my basic concept, is illustrated in block diagram form in Figure 4 and in circuit diagram form in Figure 5, comprising portions 5a, 5b and 5c. This system achieves the desired displacement of locally generated frequency between transmission and reception by using different multiples of the basic frequency generated 'by .a tunable oscillator. Under these conditions vthe difference between the initial and displaced frequencies is not a fixed frequency difference, but a ratio or percentage of the tunable oscillator frequency, so that the intermediate frequency amplifier in the receiving portion of -the system must be tuned in synchronism with tuning of the oscillator. By using different multiples of the tunable oscillator frequency on transmission and reception, the frequency at which the tuned stages of the intermediate frequency amplifier must be peaked are always identical with the frequency `being generated by the tunable oscillator. To simplify the ganging of the tuned circuits and enable exact synchronization and accurate tracking of t-he intermediate frequency tuned circuit with the oscillator tuned circuit, each of these circuits may be of exactly the same type and are designed to cover exactly the same frequency range. The coordination is effected by tracking of the variable reactance elements in the tank circuits, of course, and vis not disturbed by the addition or substraction of fixed reactance of the opposite character in switching between bands, provided only that the reactance added or substracted is of the correct value.

Referring now more particularly to Figure 4, the block diagram, the tunable oscillator A delivers its wave output to the multiplier B and the multiplier and lter arrangement here identied as T. The multiplier B" could be combined with the multiplier T in practice, if desired, although it is believed preferable to use separate multiplier arrangements for transmission vand reception, rather than switching in the same multiplier. The use of completely separate multipliers enables 'better isolation of the various parts of the circuit, and also enables switching to be done Velectronically by application or removal of plate voltage, rather than by use of a mechanical change-over switch. During transmission the desired multiple of the tunable oscillator frequency (which multiple may be anything from unity on up) is the carrier wave supplied to the power amplifier F" and modulated by the desired signals by the modulator G. When the change-over switch YD is inthe transmitting position shown in solid lines, the output of the power amplifier is delivered to the antenna system and its tuning and loading means here indicated as H.

During reception the signal picked up by the antenna and passed through the tunable antenna network Hl is delivered (the change-over switch O now being in the dotted line position) to the radio frequency amplifier J. The amplied signal is then delivered to the mixer S where it is heterodyned with locally generated waves of a desired frequency delivered from the tunable oscillator A through the multiplier and filter arrangement T. The desired beat note, which may be the difference between the incoming and local heterodyning frequencies, is then passed through the intermediate frequency amplifier K, demodulated in the detector L, and further amplified in the audio amplifier M. As in connection with the earlier systems, the tunable oscillator A" may be used as a beat frequency oscillator by closing the switch N.

It may be assumed that the oscillator A" is so designed as to be variable over a range of 1,000 to 1,500 kc. Under these conditions, if it be designed to cover the frequencies lying between .2,000 and 6,000 kc., Ithree bands would be provided, ythe multiplier B" being arranged to double on the iirst band (2,000-3,'000 kc.), triple on the next band '(3,000-4500 kc.) and quadruple on the third band (M300-6,000 kc.) Under these conditions I nd it satisfactory to provide only two different multiplying setups of the multiplier and lter arrangement T, one tripling and the other q-uadruplingr the basic frequency, as this is sufficient to enable a different multiple to be used on recept-ion in each case than the multiple used for transmission.

If it be assumed that the tunable oscillator A" was set at its lowest frequency setting and delivering a wave of a frequency of 1,000 kc., the wave output on the rst band (with the multiplier B doubling) would then be 2,000 kc., this being passed through the power amplifier' and transmitted. During reception, on the other hand, the multiplier T would be arranged to triple, so that the desired 2,000 kc. signal would be heterodyned with a local 3,000 kc. wave to give a beat note of 1,000 kc., the same as that originally generated in the tunable oscillator A. Since the 1F amplifier K is tuned to this frequency at this time (the tuning control not having been touched during the change-over from transmission to reception), the only signal reaching the antenna which will eventually reach the detector and audio amplier is the desired 2,000 kc. signal. For the three bands assumed as representative, therefore, the oscillator would cover the frequency range of 1,000 to 1,500 kc. in each case, and the tuned circuit of the intermediate frequency am- Oscillator Multiplier intermediate Band Frequency Output Frequency 1. l, OOG-l, 500 2, 000.3, 000 l. 1, 000-1, 500 3, OOO-4, 500 1, OOO-1, 500 2. l, OOO-1, 500 3, OOO-4, 500 2. l, OOO-1,50() 4, (10d-6,000 1, (10D-1, 500 3. l, OOG-1,500 4, C-6, 000 3. l, 000-1, 500 3, 0004, 500 1,0004, 500

Referring now more particularly to the circuit diagram of Figure (comprising portions 5a, 5b and 5c), a circuit for a system operating in accordance with the block diagram of Figure 4 will be described, the various portions of the circuit being lettered in correspondence with Various portions of the block diagram of Figure 4. The circuit portion identified as Figure 5u makes connection through the wires or leads, identified as a, b and c, to the circuit portion identified as Figure 5c, and through the wire identified as lc tothe circuit portion identified as Figure 5b; and this latter portion makes connection, through the wires identied as :1 to the portion identified as Figure 5c.

Referring now first to the center of the upper portion of Figure 5b, the oscillator A" is here shown as comprising a tube 60, which may be of tube type No. 12SJ7, having a tuned tank circuit comprising the permeability tuned coil El and the xed condenser 62. The output of this oscillator is delivered either to the multiplier and filter arrangement T or, through the wire 7c, to the multiplier B".

Following out rst this latter path, which would be used in transmission, and referring now more particularly to Figure 5a, it will be seen that the waves generated by the tunable oscillator are delivered to the input of a tube, here identified as 63, arranged for multiplication. The desired harmonic is selected by use of a particular one of the tuned tank circuits 64, 65 and 66 in the output of this stage, selection being effected by the band switch 61. While these tank circuits are shown as completely separate circuits comprising the xed condensers 64a, 65a and 65a on the one hand, and permeability tuned coils 64b, 65h and Elib on the other hand,` it will be understood that other A arrangements could be used in practice. Similarly, while this multiplier is shown as comprising a single stage, it will be understood that it might in practice comprise two stages. This is true of all of the various sections of the circuit diagram, the number of tubes in each section generally being less than would be the case in actual commercial sets, which would generally have several stages of RF amplication, several stages of IF amplification, several stages of pre-amplification ahead of the' last or power output stage for transmission, etc. Further following out the operation of the systern during transmission, the desired multiple of the original wave provided by the multiplier B is delivered to a power amplifier here shown as comprising only a single stage comprising the tube 63, which may be of tube type No. `1625. When the change-over switch O" is inl the position shown in solid lines, the output of this tube is delivered to the antenna tank circuit here shown as comprising the variable inductance 69 and whichever one of the condensers lea-c is selected by the band switch ll. The tank circuit is in turn coupled to the antenna system through appropriate loading means here shown as comprising the tapped coil l2 and the Variometer 13. The band switches are all shown in the second position so that, if the tunable oscillator were set to deliver 1,000 kc., as assumed earlier, the transmitted frequency would be 3,000 kc. This carrier frequency would be combined with the desired signal by the modulator G shown in the upper right-hand corner of Figure 5c. Sounds supplied to the microphone 'ld are delivered to the input of the first stage of the modulator, comprising the tube here identified as 15, which may be of tube type No. 12SF5. This tube is here shown as working into a push-pull output stage comprising a pair of tubes 1b and l1, which may be of tube type No. 1625. The output of these latter tubes is connected (through the wire b) in conventional manner for plate modulation of the power amplier output.

When it is desired to receive on the same frequency as that on which transmission has taken place, a change-over from transmission to reception would be made without changing the tuning controls, this change-over including movement of the switch O" from the position shown in solid lines in Figure 5a to the position shown in dotted lines. `In this latter position signals received by the antenna system and subjected to at least preliminary selection in the tuned portion of the antenna network H" are delivered (through the wire a) to the radio frequency arnplifier J here shown as comprising tbe single tube 19 in the lower right-hand corner of Figure 5c, which tube might be of tube type No. 12SG7. The output of this tube includes one of three tuned tank circuits selected by the band switch 80, the tank circuits comprising the variable inductances Bla, 82a. and 83a and the xed condensers SIb, 82h and 83h, respectively. The waves subjected to preliminary selection by these tuned circuits in the input and output of the radio frequency amplifier are then delivered to the signal grid of the mixer tube here identiiied as 34, which may be of tube type No. 12SA'7. Here it is heterodyned with what are being termed the displaced frequency desired waves, and the source of these waves will now be described.

Referring now briefly back to Figure 5b. it will be recalled that the wave output of the tunable oscillator A (comprising the tube and its associated circuits) is also delivered to the other multiplier T not heretofore described. This multiplier is here shown as comprising a tube which may be of tube type No. 12SG7, having its plate current supply derived from the wire at the Very bottom of this figure (this wire being identified as i). Referring now more particularly to Figure 5c again, it will be seen that this platesupply lead Wire is connected to one of two contact points of a plate supply change-over switch here identified as 'l. The movable element of this two-position switch is synchronized with movement oi the change-over switch G, so that plate supply voltage from the generatora 88 is delivered to the multiplier B", the power amplier F and the modulator G only when the switch is in the position shownin solid lines in thisA figure. On the other hand, when` the; switch is; thrown to.v the dotted linev position for reception, now being described, the other multiplier T"", and.: the various tubes in the receiving portion. of the system, are energized. rEhe wire identied as f provides plate voltage at all times for the oscillator A, so thatV this operates during both` transmissionl and reception. Throwing the system overv to` receiving condition, therefore, causes electronic switching from one multiple to another, so that the system can be conveniently arranged toy provide a different multiplicationv or" the basic oscillatorl frequency during reception from that usedv during transmission'. The output of the multiplier tube St (Figure 5b): is delivered through the'wire d and the band: switches E and :l0: to one ci' two` chosen ltersystems 'nereshown as comprising only two stages; a1-

though in practice they would normally comprise rive stages to secure the desired amount of attenuation of unwanted harmonics. With the band switches 09 and 90' in the second band position (3,000-4,500 kc), the lower nlter network here identified in general as Si is operative, the output of this filter network being delivered to the injection grid of the mixer tube S0; Under the conditions assumed in the table given in connection with the description of the block diagram of Figure c, this filter network would` be arranged to quadruple when the set was operating on the second band (3h00-4,500 kc), the variable reactance elements of this ilter being ganged with the other tuned portions of' the circuit to provide quadruple the frequency regardless of the setting of the tunableoscillator. The other cr upper filter network, herev identified in general as 92, is arranged for tripl-ing and is operative on both thefirst and thirdbands ciescribed. ln any case, the output of these hlt-er networks is a multiple of the basic oscillator fre-- ouency one removed-from that 'sed during transmission, so that one of the resultant beat notes in the'cutput of the mixer tube @Il is av frequency identical with that of the original timable oscillator frequency.

Referring now morev particularly to lgurel 5 it will be seen that theoutput of mixer tubev d through wire g to' the input oi an' interndiam amplier here Slifer-.iif as com'- prising only a single stage, although as has been mentioned before, several stages would be used in: practice. This stage is here shown as cornprising a tube which may be oftubc type No. lZSGl, with input and output tuning: networks which are tunable and which areY also ganged with the tuning of the oscillator A. The input tuning is here shown as comprising two condenser coupled parallel tank circuits-comprising the variable inductance 9130, and the hired capacity till) on the one hand and the variable inductance 05a and ii'xed capacity on the other hand; and the output is tuned by a similar network comprising the variable inductance @to and' fixed condenser Sith as one tank circuit and the variable inductance Sla and xcd condenser @lo as the other tank circuit. Theoutput of the intermediate frequency amplifier isI delivered to the detector stage comprising the rectierv tube which may be of tube type No. 12H6, where the signal is demodulated and where it may be heterodyned against the original oscillator frequency for beat note purposes, if desired, by closing the switch N The detector output is then delivered to the audio amplifier lvl, here shownas comprising onlya` single stage. consist- 16 ing of the tube 991,. which maybe of tube type No.; lZAG, transformer coupled through a manually variable volume control to the translating device here shown as'earphones itil.

An operative circuit of the character described, fory thel bands and frequency ranges previously assumed, might have the circuit element values which will now be described, nductance being given in microhenries, capacities in micro-microfarads and resistance in ohms. The permeability tuned oscillator tank circuit inductance (il might be variable from liv-25.5; the transmitter multiplier inductances 64b, 05h and 56h might vary from 17-7.8, lll-6.2 and 1li-6.2, respectively, The antenna tank circuit coil E9 might be variable from 6.6-2.9; the tunable coils in the filter section 9| of the receiver multiplier, and the coil 33a in the RF amplifier might be variable from 7.3-3.3; the. tunabley coils in the section 92 of the receiver multiplier lteigandlthe coil 82a in the RF amplifier might be variable from 9.4-4.2; the rst band coil Bla. in the RF amplier might be variable from. l3.5-6; and: the IF amplier tuned coils 94a,` 95a, 96a and 97a might be variable from 59-26 microhenries. Under these circumstances the oscillator tank circuit condenser 62 might have a capacity of 1,000. micro-microiarads; the transmitter multiplier', condensers @5a and 66a might have capacities of 357, 200 and 113, respectively, for the bands assumed; the antenna network. tank circuit condensers lila, 10b and 10c might. have capacities of 683, 26-1 and 208, respectively; the tank circuit condensers in the section 9! of the. receiver multiplier filter, and the. condenser 33h in the RF ampliiier, might have capacities of 216; the tank circuit condensers in. the lter section Q2 of the receiver multiplier,l and the condenser bin the RF ampliiier, might. have capacities or 300; the rst bancltank circuit condenser 8l b in the RF amplilier might havea capacity of 465; and the tank circuit condensers 9th, 95h, 05o and @lb in the IF amplier might have capacities of 430 micromicrofarads.

Other circuit constants would be of conventional value for the particular tubes used and the functions desired of those tubes. The coupling condensers in the oscillator input, the receiver multiplier output, and the RF amplifier might have a capacity of the coupling condensers connecting the oscillator and th-e transmitter multiplier, the power amplier and the antenna network, and the detector and AF amplier might have a capacity of 2,000; and the coupling condenser between the transmitter multiplier tube andthe band switch El, and between that switch and the input of the power ampliher might be 500 and 800, respectively. The coupling condensers between sections of the filter networks in the receiver multiplier output, and those between the tank circuit sections in the intermediatet frequency amplier, might have a capacity of 10 micro-microfarads; while the coupling condensers between the tubes 84 and 93 and the tuned sections to which these tubes are coupled might be350. Thescreen grid bypass condensers for the tubes 60, 63,y '19, 84, 30 and S3, and the cathode resisterV bypass condensers for the tubes 7.9, 84 and 93, might have capacities of 10,000 micro-microfarads; and the cathode resister bypass condensers for the tubes 15, lt, lll and 539A might have capacities of l microfarads. The oscillator screen grid and grid leak resistere might have values of 68,000 and 50,000 ohms, respectivelyrthe tubesl and 93. might have screen grid'resisters of 100,000 ohms each; the receiver multiplier tube 86 might have a screen grid resistance of 680,000 ohms; and the miXer tube 84, one of 330,000 ohms. The power amplifier tube 68 might have signal grid and screen grid resisters of 10,000 ohms each; the RF amplifier tube 19 might have a grid leak resister of one megohm, and the multiplier tube 86 a grid leak resister of 47,000 ohms; the modulator tubes 16 and ll might have a single cathode bias resister of 125 ohms, and the tube 'l5 one of 1,600 ohms; and the tubes 19, 84, 93 and 99 might have cathode resisters of 100, 470, 150 and 1,600 ohms, respectively, while as much as one megohm, bypassed by 250 micro-microfarads, might be used in the cathode lead of the detector tube 98. It will be understood that these values are given asV representative only to enable quicker and more convenient construction of radio apparatus conforming to the circuit shown in Figure and that'in practice these values would be varied in known manner depending upon the exact plate voltages used and 'other factors. Radio frequency chokes, blocking resisters, transformers, and other circuit elements not specifically described would follow conventional practice in connection with the particular function of the types of tubes specically named as representative.

While I have shown and described certain embodiments of my invention, it is to be understood that it is capable of many modications.

I claim:

l. Radio apparatus of the character described, including: tunable means for generating unmodulated waves of a first high frequency which may be continuously varied over a predetermined range; multiplying means operative upon said waves for providing rst desired unmodulated waves of a high frequency comprising a predetermined multiple of "said first frequency and second desired unmodulated waves of a high frequency comprising a different multiple of said first frequency; means for amplifying and transmitting one of the desired waves; and a super-- heterodyne receiving system having an `intermediate frequency amplifier tuned to the difference between the frequencies of the two desired waves, the desired Waves which were-not transmitted serving as the local heterodyning waves for said receiving system to provide for the reception of signals of the same `frequency as the transmitted waves.

2. Radio apparatus of the character described, including: tunable means for generating waves of a rst frequency variable over a predetermined range; multiplying means for providing first desired waves of a frequency comprising a predetermined multiple of said first frequency and second desired waves of a frequency comprising a different multiple of said first frequency; means for amplifying and transmitting one of the desired waves; and a super-heterodyne receiving system having a tunable intermediate frequency amplifier tunable over the same range as and coordinated with said tunable means, the other of said desired waves serving as the local heterodyning waves for said receiving system.

3. Radio apparatus of the character described, including: tunable means for generating waves of a first frequency variable over a predetermined range; multiplying means for providingA rst desired waves of a frequency comprising a predetermined multiple of said first frequency and second desired waves ofal frequency com- CSi prising a diiferentmulti le of said first frequency; means for amplifying and transmitting one of the desired Waves; a super-heterodyne receiving system having a tunable intermediate frequency amplifier tunable over the same range as and coordinated with said tunable means;

and selectively operable means for connecting the multiplier to the amplifying means on the one hand and for providing a multiplication different by one from that usedfor transmission and connecting the multiplier to the receiving system on the other hand, whereby the waves resulting from said different multiplication serve as the local heterodyning waves for said receiving system.

4. Radio apparatus of the character described, including: tunable means for generating waves of af'rst frequency variable over a predetermined rarige; a first multiplier for providing first desired waves of a frequency comprising a predetermined multiple of said first frequencyy asecond multiplier for providing second desired Waves of a frequency comprising a different multiple of said first frequency; means for amplifying and transmitting one of the desired waves; a super-heterodyne receiving system having a tunable intermediate frequency amplifier tunable over the same range as and coordinated with said tunable means; and selectively operable means for connecting the first multiplier to the amplifying means on the one hand and for connecting the second multiplier to the receiving system on the other hand, whereby the waves resulting from said different multiplication serve as the local heterodyning waves for said receiving system.

5. Apparatus of the character claimed in claim' 4, wherein each of said multipliers is adapted to provide a plurality of multiplications and coordinating means causes said second multiplier' to provide a multiplication different by one from that at which the first multiplier is operating.

6. Radio apparatus of the character described, including: tunable means for generating waves of a first frequency variable over a predetermined range; multiplying means for providing iirst desired waves of a frequency comprising a predetermined multlple of said rst frequency and second desired `waves of a frequency comprising a different multiple of said 4,first frequency; an

antenna system comprising an antenna and tunnecting the multiplier to the input of the amplifying means and the antenna system to the output thereof on the 'one' hand and for providing a multiplication different by one from that used for transmission and connecting the antenna `system and the multiplier to the receiving system on the other hand, whereby the waves resulting from said different multiplication serve as the local heterodyning waves forsaid receiving system.

'7. Radio communication apparatus of the char# acter described, including: variable wave generating means for providing desired waves of an' initial frequency variable over a predetermined range; means for providing other desired waves of a frequency displaced from the initial frequency, this means including said wave generating means; means'for amplifying and transmitting one 'f the desired Wavesa super-heterodyna aser/srs receiving-'f'- system havi'rg an intermediate frequency amplifier tuned to'l th'e difference' between the' fr''eq'fue'nc'iesl of the?v c' desired Waves, the desired v'v'ave's which were noti transmitted serving'- as the. local heterodynmg waves for said rec'eivingf system, sai-'dl s'yster'n also having a seconddetecto'r'conne'cted to' said intermediate frequency ar'riplier; and a' circuit including' switch means for? selectively' connecting one o'f said two first mentioned means' to sardi second detector fm.` heterodyning the waves; ofi said selected means with` the' intermediate frequency' waves to provide a beat frequency' note during' reception of unmodulated si'giials'i- 8. Radio apparatus of the character described, including: variable v'ven'e"` generating means for providing" desiredY waves of an*- initial frequency'I variable" over a predetermined'. range; a second dsllltr' for' grel'l Waves f a Xed frequency; means fo'r m Xing' said wayes and providingf, witlficut varia ioniV ofi` said; tunable oscillatory other? desired w v'e's" of a frequency displaced from the initialt "equency by said fixed frequency; means for ampl` "ng and transmitting? one of the' desired' Waves; al super-heterodyne receiving systemf having' arr intermediateY frequency" amplifier tuned tothe difference between the frequencies of the' twoiv desired waves, the desired waves' which` were not transmitted serving as the locali heterodynin'g waves for said receiving system, said system also having a second detector connected. t'd said; intermediate frequency amplifier; and circuit includingY switch means for selectively cennecting said fixed frequency oscillator to' said. second detector for heterodyning the Waves generated by said fixed frequency oscillator with the intermediate frequency waves to provide a beat' frequency note during' code' reception.-

9". R'adio" apparatus of the character described, includingi tunable I'ne'an's for" generating waves` of a rst frequency variable over apredetermined range; multiplying means for providing first desired waves of afrequency comprising? a pre'- determined' multiple' of said first frequency and second desired waves of a frequency comprisingl al different multiple of said first frequency means for' amplifying and transmitting one of the desired waves; a 'super-heterodynereceiving system having an intermediate frequency ampli-lier tuned to the difference between the frequencies of the two desired waves,` the desired waves which were' 'not transmitted serving as the local heterodyning waves for said receiving system., said system also" having a second detector connected` thel intermediate frequency` waves to provide abeat frequency note during reception.

11. Radio communication apparatus of the character described, including: a manually tunable' oscillator' for generating desired radio frequency waves of an initial frequency which may be varied uninterruptedly over a predetermined range; means associated with said oscillator for 20 providing.` Without variation' of' said. oscillator.'` other desired radioy frequency waves of a. fre'- quency displaced fromv the initial frequency but bearing a predetermined. relation thereto; means for amplifying and transmitting one of the cle-- sir'ed' waves;l a super-,heterodyne receiving sys?-` tem having an intermediate frequency amplifier tuned' to the difference between the frequencies of the-two desiredzwaves, the desired waves which were not transmitted serving as the local heterodyning waves for said receiving system; and switching means for selectively rendering inoperable at least a' portionof the amplifying. means of the transmitting means; during' recep-; tion and at least a portion of the receiving. sys-- tem during transmission to provide for' reception of. signals of the same frequency as the transf` mitted. Waves.

1-2. Radio communication apparatus of the character described, including.: a manually tuny able: radio frequency oscillator for generating. desired waves of anV initial frequency which may be varied uninterruptedly over a predetermined. range; means associated with said. oscillator for' providing, without variation of said oscillator..V other desired waves of a frequency displaced from the initial frequency by a predetermined: frequency, this means including said tunable oscillator; means for amplifying and transmittingone of the desiredwaves; a super-heterodyne receiving system having an intermediate frequency amplifier tuned to the diiierence'between, the frequencies of the two desired waves, the desired waves which were not transmitted serving as the local heterodyning waves for said re.- ceiving system; and switching means for selectively deenergizing at least a portion. of the amplifying means of the transmitting means during reception and at least a' portion of said receiving system during transmission, to provide for reception of signals of the same frequency' as the transmitted waves.

13. Radio communication apparatus of thev f 1 ing of said oscillator, other desired radio fre-y quency waves of a frequency displaced from the initial frequency but bearingv a predetermined relation thereto; means for amplifying' and transmitting one of the desired Waves; a super-heterodync receiving system having an intermediate frequency amplifier tuned to the difference between the frequencies of the two desired waves, the desired waves which were not transmitted serving as the local heterodyning waves for said receiving system; and switching means for selec'-` tively rendering inoperable at least a portion of the electronic portion of the transmitting means during reception to provide for reception of signalsv of the same frequency as the transmitted FRANK M. DAVIS.

Number Date (Other references on following page) Chaffee Nov. 25, 1941 Number 21 UNITED STATES PATENTS Name Date Hallborg et a1 Aug. 26, 1924 Young Apr. 5, 1938 Rochow Jan. 24, 1939 Chaee Mar. 18, 1941 Brown June 17, 1941 Slonczewsk Aug. 19, 1941 i Leyn May 5, 1942 Martin July 14, 1942 McRae Apr. 27, 1943 Case Aug. 17, 19`43 Davis June 25, 1946 Goldsmith Sept. 23, 1947 Number 22 FOREIGN PATENTS Country Date Germany May 8, 1910 Great Britain Feb. 24, 1943 OTHER REFERENCES The A. R. R. L. Antenna Book, published 1942 by The American Radio Relay League, Inc., West Hartford, Conn., pages 138-141 relied on, pages 10 21-29 to show the state of the art. 

